The invention relates to a measuring device for identifying the enveloping cylinder of precision round parts, particularly of light waveguide plug pins.
In optical communication transmission systems using light waveguides, optical fibers are coupled together by mechanically ultra-precise plug connectors so that the two signal-carrying fiber cores meet one another coaxially with sub-micrometer range precision and, thus, guarantee a minimum signal attenuation. It is highly desirable that precision dimensions of plug pins and plug sleeves are maintained in order to conform to mnufacturing tolerances in the sub-micrometer range for diameter and cylindrical shape. Such precision is usually far beyond present measuring techniques. Another complicating factor is that the fabrication of the plug pins within the plug sleeve is just as problematical, so that no ideal or more easily measurable test method presently exists. That means that the measuring method must be selected so that functionally unimportant inadequacies of the plug pins do not lead to their rejection.
Sophisticated manipulation of conventional metrology still just barely suffice given previously fabricated plug components which did not require such a tolerance. For high-precision parts, involved measurements with high-precision universal measuring instruments of a precise measuring space were carried out on a few units or an attempt was made to "sense" the usability with the best possible gauges. An inspection of the plug pins for pluggability requires the identification of the enveloping cylinder, i.e. of the smallest possible enveloping cylinder upon consideration of the roundness and straightness deviations of a pin. This can be best implemented with a testing device which meets Taylor's principle, i.e. for a quality check, every surface element of the fitting surface of the unit under test must have a suitable surface element of the test installation residing opposite it. In the case of plug pins, this principle was previously met by means of a test using gauge rings. Gauge rings, however, are not available in the required, fine diameter gradations. Moreover, commercially available gauge rings would wear too quickly.